sched domains oddness. - Kernel

This is a discussion on sched domains oddness. - Kernel ; The attached dmesg comes from my dual core laptop running 2.6.27
What's up with all the sched domains transitions at the bottom?
This was just a boot up from power off, no suspend/resume or anything funky.
Dave
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http://www.codemonkey.org.uk
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sched domains oddness.

The attached dmesg comes from my dual core laptop running 2.6.27
What's up with all the sched domains transitions at the bottom?
This was just a boot up from power off, no suspend/resume or anything funky.

Re: sched domains oddness.

On Fri, Oct 31, 2008 at 10:09:29AM -0700, Suresh Siddha wrote:
> > looks like someone is triggering rebuild_sched_domains(), is something
> > poking cpusetfs files or flipping between sched_mc settings?
>
> I remember someone mentioning that some distro's started setting
> sched_mc_power_savings to '1' by default during boot. On a dual-core
> laptop, this will not give any advantage.
>
> I have to fix the code to not export this tunable, when we have only
> socket in the system.
>
> Dave, Is your distro also setting this tunable blindly during boot

Re: sched domains oddness.

On Fri, Oct 31, 2008 at 01:17:21PM -0400, Dave Jones wrote:
> On Fri, Oct 31, 2008 at 10:09:29AM -0700, Suresh Siddha wrote:
>
> > > looks like someone is triggering rebuild_sched_domains(), is something
> > > poking cpusetfs files or flipping between sched_mc settings?
> >
> > I remember someone mentioning that some distro's started setting
> > sched_mc_power_savings to '1' by default during boot. On a dual-core
> > laptop, this will not give any advantage.
> >
> > I have to fix the code to not export this tunable, when we have only
> > socket in the system.
> >
> > Dave, Is your distro also setting this tunable blindly during boot
>
> (13:15:25:davej@vaio:~)$ cat /sys/devices/system/cpu/sched_mc_power_savings
> 0
>
> So no, unless something set it to 1, and then back to 0.
>
> A grep of etc shows up nothing in initscripts. Does hal or something
> play with this?

Even curiouser.. When I unplug AC and replug it, it happens again, but slightly
differently..

This is def coming from sched_mc_power_savings. Some battery script
or something is getting notified and setting this value. Can you do
a grep from / for sched_mc_power_savings ?
> This still doesn't explain the flip-flop I saw just from booting,
> as that was on AC the whole time.

Boot messages are def something not related to sched_mc_power_savings.

So I found something (pm-utils) that seems to have mechanism for changing sched_mc
Though it's not obvious to me how this is getting invoked.
One question I have though is that to set this sensibly, it seems that
userspace is going to have to have understanding of how the topology is
layed out. Given the kernel already knows, perhaps not making that
sysfs file present on systems where it doesn't make sense would be simpler ?